In wireless mobile devices, conventional non-linear control system for automatic frequency control (AFC) of a voltage-controlled oscillator (VCO) is required for synchronization with a received radio frequency channel. This requires frequent switching or correction depending on the operating state of the wireless device. Variability in the RF channel quality during different phases such as initialization, cell hand-offs or deep channel fades can require frequent switching back and forth between control states which can lead to instability and phase jitter in the tracking process. In VCO control system the adjustment of the filter coefficients in the adaption process has to ensure optimum tracking performance for both transient and steady state response as well as stability. The inability to provide the appropriate filter coefficients based upon the current operating state in the wireless devices results in processing delays and inefficient resource utilization.
Accordingly, methods and apparatus that enable improved automatic frequency control remains highly desirable.
It will be noted that throughout the appended drawings, like features are identified by like reference numerals.